Inkjet printers include an ink path from an ink supply to a print head that includes nozzles from which ink drops are ejected. Ink drop ejection can be controlled by pressurizing ink in the ink path with an actuator, for example, a piezoelectric deflector, a thermal bubble jet generator, or an electrostatically deflected element. A typical print head has a line or an array of nozzles with a corresponding array of ink paths and associated actuators, and drop ejection from each nozzle can be independently controlled. In a so-called “drop-on-demand” print head, each actuator is fired to selectively eject a drop at a specific location on a medium. The print head and the medium can be moving relative one another during a printing operation.
In order to achieve larger print widths many commercial inkjet printers comprise print bars that include a mounting assembly and a plurality of print heads that are mounted to the mounting assembly and that are typically arranged in linear or staggered relationship. A printer may include a plurality of print bars.
To give an example, US 2007/0070103 A1 (Konica Minolta) relates to a line type inkjet printer wherein a plurality of ink nozzles are arranged over a length corresponding to the width of a printing medium. It comprises a drive signal generating circuit for each head that outputs the signal for emitting the ink particles at a timed interval confirming to a timing signal. The line head is provided with a plurality of head modules in staggered arrangement, each head module being made up of a set of a plurality of print heads, each head having a head position adjusting mechanism. Ink is fed to an intermediate tank by means of a pressure pump. From the intermediate tank the ink passes a filter and is fed to an ink flow path that is common to all the head modules. The document suggests to replace only the print head instead of entire head modules. Thanks to the head position adjusting mechanism the time required for readjustment of the replaced head is reduced.
Having a central ink supply for all the print bars, spare parts for the central supply as well as for the local print bars and print heads, including the print heads themselves, must be held available. Furthermore, designing a specific printer and in particular its central ink supply in such a way that all print heads are reliably supplied with ink from an ink cartridge via an intermediate tank and comparably long conducts is a demanding task, especially if high printing frequencies shall be achieved. This means that both designing and building a new printer having a configuration that differs from a previously designed printer as well as maintenance of the printer is time consuming and expensive.